Chapter 6 b Communication Integration and Homeostasis Novel

Chapter 6 b Communication, Integration, and Homeostasis

Novel Signal Molecules: Calcium • Calcium as an intracellular messenger Extracellular fluid Electrical signal Voltage-gated Ca 2+ channel opens. released from intracellular Ca 2+ stores Ca 2+ in cytosol increases. Ca 2+ binds to proteins Chemical signal Calmodulin Other Ca 2+binding proteins Intracellular fluid Alters protein activity Exocytosis Movement Figure 6 -15

Novel Signal Molecules: Calcium Extracellular fluid Electrical signal Voltage-gated Ca 2+ channel opens. Intracellular fluid Figure 6 -15 (1 of 5)

Novel Signal Molecules: Calcium Extracellular fluid Electrical signal Voltage-gated Ca 2+ channel opens. released from intracellular Ca 2+ stores Chemical signal Intracellular fluid Figure 6 -15 (2 of 5)

Novel Signal Molecules: Calcium Extracellular fluid Electrical signal released from intracellular Ca 2+ stores Voltage-gated Ca 2+ channel opens. Ca 2+ in cytosol increases. Chemical signal Intracellular fluid Figure 6 -15 (3 of 5)

Novel Signal Molecules: Calcium Extracellular fluid Electrical signal Voltage-gated Ca 2+ channel opens. released from intracellular Ca 2+ stores Chemical signal Ca 2+ in cytosol increases. Ca 2+ binds proteins Calmodulin Other Ca 2+binding proteins Intracellular fluid Figure 6 -15 (4 of 5)

Novel Signal Molecules: Calcium Extracellular fluid Electrical signal Voltage-gated Ca 2+ channel opens. released from intracellular Ca 2+ stores Ca 2+ in cytosol increases. Ca 2+ binds proteins Chemical signal Calmodulin Other Ca 2+binding proteins Intracellular fluid Alters protein activity Exocytosis Movement Figure 6 -15 (5 of 5)

Novel Signal Molecules: Gases • Nitric oxide (NO) • Activates guanylyl cyclase • Formation of c. GMP • Acts as neurotransmitter and neuromodulator in brain • Produced by endothelial cells • Diffuses into smooth muscle and causes vasodilation

Novel Signal Molecules: Gases • Carbon monoxide (CO) • Also activates guanylyl cyclase and c. GMP • Targets smooth muscle and neural tissue • Hydrogen Sulfide (H 2 S) • Targets cardiovascular system • Garlic is major source of precursors

Novel Signal Molecules: Lipids • The arachidonic acid cascade produces lipid messengers Figure 6 -16

Novel Signal Molecules: Lipids • Leukotrienes • Role in asthma and anaphylaxis • Prostanoids • Prostaglandins • Sleep, inflammation, pain, fever • Thromboxanes • Nonsteroidal anti-inflammatory drugs (NSAIDs) help prevent inflammation by inhibiting cyclooxygenase (COX)

Modulation of Signal Pathways • Specificity and competition • Agonist versus antagonist • Multiple receptors for one ligand • Alpha receptor • Vasoconstriction • Beta receptor • Vasodilation

Modulation of Signal Pathways • Agonist versus antagonist The primary ligand activates a receptor. An agonist also activates the receptor. Response An antagonist blocks receptor activity. No response Figure 6 -17

Modulation of Signal Pathways • Target response depends on the target receptor -Receptor response -Receptor Intestinal blood vessel Epinephrine + -Receptor 2 -Receptor response 2 -Receptor Skeletal muscle blood vessel Epinephrine + 2 -Receptor Vessel constricts Vessel dilates Figure 6 -18

Modulation of Signal Pathway • Up-regulation • Down-regulation • By decreasing the number of receptors • By decreasing the binding affinity • One explanation for drug tolerance • Termination mechanism • Disease and drugs

Modulation of Signal Pathway • Disease and drugs target signal transduction proteins Table 6 -3

Control Pathways: Overview • Physiological control systems keep regulated variables within a desired range during homeostasis Regulated variable influence Within desired range Outside desired range Effectors CONTROL SYSTEM No action required Sensor is activated sends signal to alters Integrating center Figure 6 -19

Control Systems: Cannon’s Postulates 1. 2. 3. 4. Nervous regulation of internal environment Tonic control Antagonistic control One chemical signal can have different effects in different tissues

Control Systems: Tonic Control • Tonic control of blood vessel diameter Tonic control regulates physiological parameters in an up-down fashion. Electrical signals from neuron Time Change in signal rate Increased signal rate Time Decreased signal rate Time Figure 6 -20

Control Systems: Antagonistic Control Antagonistic neurons control heart rate: some speed it up, while others slow it down. Parasympathetic neuron Stimulation by sympathetic nerves increases heart rate. Heart beats Sympathetic neuron Stimulation by parasympathetic nerves decreases heart rate. Heart beats Figure 6 -21

Control Pathways • Comparison of local and reflex control Brain evaluates the change and initiates a response. Brain Systemic change in blood pressure sensed here. LOCAL CHANGE Blood vessels LOCAL RESPONSE REFLEX RESPONSE is initiated by cells at a distant site. KEY Stimulus Integrating center Response Figure 6 -22

Control Pathways: Reflex Control Feedback loop • Steps in a reflex control pathway STIMULUS SENSOR or RECEPTOR AFFERENT PATHWAY Response loop INTEGRATING CENTER EFFERENT PATHWAY TARGET or EFFECTOR RESPONSE Figure 6 -23

Control Pathways: Receptors • Multiple meanings of the word receptor RECEPTORS can be Cell membrane or intracellular receptor proteins Specialized cells or structures that convert various stimuli into electrical signals Central receptors are in or close to the brain. Eyes (vision) Ears (hearing, equilibrium) Nose (smell) Peripheral receptors lie outside the brain. Tongue (taste) Other Chemoreceptor Osmoreceptor Thermoreceptor Baroreceptor Proprioceptor mechanoreceptors (p. H, gases, (body position) (pain, vibration, (osmolarity) (temperature) (pressure) chemicals) touch) Figure 6 -24

Control Pathways: Response Loop Reflex steps • A nonbiological response loop 1 Water temperature is 25° C 2 Wire 4 Control box 6 Heater 5 STIMULUS 2 Thermometer senses temperature decrease. SENSOR or RECEPTOR 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 4 Control box is programmed to respond to temperature below 29 degrees. Thermometer 7 Water temperature increases 1 Water temperature is below the setpoint. INTEGRATING CENTER 3 5 Signal passes through wire to heater. EFFERENT PATHWAY 6 Heater turns on. TARGET or EFFECTOR 7 Water temperature increases. RESPONSE Wire to heater Figure 6 -25

Control Pathways: Response Loop Reflex steps 1 Water temperature is below the setpoint. STIMULUS 1 Water temperature is 25° C Figure 6 -25, step 1

Control Pathways: Response Loop Reflex steps 1 Water temperature is 25° C 1 Water temperature is below the setpoint. STIMULUS 2 Thermometer senses temperature decrease. SENSOR or RECEPTOR 2 Thermometer Figure 6 -25, steps 1– 2

Control Pathways: Response Loop Reflex steps 1 Water temperature is 25° C 1 Water temperature is below the setpoint. STIMULUS 2 Thermometer senses temperature decrease. SENSOR or RECEPTOR 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 2 Thermometer Wire 3 Figure 6 -25, steps 1– 3

Control Pathways: Response Loop Reflex steps 1 Water temperature is 25° C 2 STIMULUS 2 Thermometer senses temperature decrease. SENSOR or RECEPTOR 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 4 Control box is programmed to respond to temperature below 29 degrees. Thermometer Wire 1 Water temperature is below the setpoint. INTEGRATING CENTER 3 4 Control box Figure 6 -25, steps 1– 4

Control Pathways: Response Loop Reflex steps 1 Water temperature is 25° C 2 4 Control box STIMULUS 2 Thermometer senses temperature decrease. SENSOR or RECEPTOR 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 4 Control box is programmed to respond to temperature below 29 degrees. Thermometer Wire 1 Water temperature is below the setpoint. INTEGRATING CENTER 3 5 Signal passes through wire to heater. EFFERENT PATHWAY 5 Wire to heater Figure 6 -25, steps 1– 5

Control Pathways: Response Loop Reflex steps 1 Water temperature is 25° C 2 4 Control box 6 Heater 5 STIMULUS 2 Thermometer senses temperature decrease. SENSOR or RECEPTOR 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 4 Control box is programmed to respond to temperature below 29 degrees. Thermometer Wire 1 Water temperature is below the setpoint. INTEGRATING CENTER 3 5 Signal passes through wire to heater. EFFERENT PATHWAY 6 Heater turns on. TARGET or EFFECTOR Wire to heater Figure 6 -25, steps 1– 6

Control Pathways: Response Loop Reflex steps 1 Water temperature is 25° C 2 Wire 4 Control box 6 Heater 5 STIMULUS 2 Thermometer senses temperature decrease. SENSOR or RECEPTOR 3 Signal passes from sensor to control box through the wire. AFFERENT PATHWAY 4 Control box is programmed to respond to temperature below 29 degrees. Thermometer 7 Water temperature increases 1 Water temperature is below the setpoint. INTEGRATING CENTER 3 5 Signal passes through wire to heater. EFFERENT PATHWAY 6 Heater turns on. TARGET or EFFECTOR 7 Water temperature increases. RESPONSE Wire to heater Figure 6 -25, steps 1– 7

Control Pathways: Setpoints • Oscillation around the setpoint • Acclimatization refers to natural adaptation • Acclimation refers to induced adaptation Negative feedback turns response loop off Setpoint of function Normal range of function Response loop turns on Figure 6 -26

Control Pathways: Feedback Loops • Negative and positive feedback • Feedforward control refers to anticipatory responses • The response counteracts the stimulus, shutting off the response loop Initial stimulus Response loop shuts off Response Stimulus (a) Negative feedback Figure 6 -27 a

Control Pathways: Feedback Loops • The response reinforces the stimulus, sending the varible farther from the setpoint Initial stimulus Response Feedback cycle An outside factor is required to shut off feedback cycle. Stimulus (b) Positive feedback Figure 6 -27 b

Control Pathways: Feedback Loops Baby drops lower in uterus to initiate labor Cervical stretch causing stimulates Push baby against cervix Oxytocin release Positive feedback loop causes Uterine contractions Delivery of baby stops the cycle Figure 6 -28

Control Pathways: Setpoints • Circadian rhythms (a) Figure 6 -29 a

Control Pathways: Setpoints 9: 00 A. M. (b) Figure 6 -29 b

Control Systems: Speed and Specificity Table 6 -4

Control Pathways: Review A simple endocrine reflex A simple neural reflex A complex neuroendocrine reflex Internal or external change Receptor Afferent path: sensory neuron Endocrine system sensorintegrating center Neural system integrating center Efferent signal: hormone Efferent neuron or neurohormone Effectors Endocrine integrating center Response Efferent signal # 2: hormone Effectors Response Figure 6 -30

Control Pathways: Review • Some basic patterns of neural, endocrine, and neuro-endocrine control pathways Neurohormone reflex Simple neural reflex 1 Stimulus Simple endocrine reflex Neuroendocrine reflexes 2 3 4 5 6 Stimulus Stimulus Receptor Afferent neuron Neurotransmitter Efferent neuron Neurotransmitter Neurohormone Response Target cell Response Blood vessel Endocrine cells Hormone Response KEY Stimulus Receptor (sensor) Sensory neuron (afferent pathway) CNS integrating center Endocrine integrating center Efferent pathways Efferent neuron Hormone #2 Response Neurotransmitter Neurohormone Classic hormone Target cell (effector) Response Figure 6 -31

Control Pathways: Review Simple neural reflex 1 Stimulus Receptor Afferent neuron Efferent neuron Neurotransmitter Target cell Response KEY Stimulus Efferent pathways Receptor (sensor) Efferent neuron Sensory neuron (afferent pathway) Neurotransmitter CNS integrating center Endocrine integrating center Neurohormone Classic hormone Target cell (effector) Figure 6 -31, step 1

Control Pathways: Review Simple neural reflex Neurohormone reflex 1 2 Stimulus Receptor Afferent neuron Efferent neuron Neurotransmitter Target cell Blood vessel Response KEY Stimulus Efferent pathways Receptor (sensor) Efferent neuron Sensory neuron (afferent pathway) Neurotransmitter CNS integrating center Endocrine integrating center Neurohormone Classic hormone Target cell (effector) Figure 6 -31, steps 1– 2

Control Pathways: Review Simple neural reflex Neurohormone reflex 1 2 Stimulus Neuroendocrine reflexes 3 Stimulus Receptor Afferent neuron Efferent neuron Neurotransmitter Target cell Blood vessel Response KEY Stimulus Efferent pathways Receptor (sensor) Efferent neuron Sensory neuron (afferent pathway) Neurotransmitter CNS integrating center Endocrine integrating center Neurohormone Classic hormone Target cell (effector) Figure 6 -31, steps 1– 3

Control Pathways: Review Simple neural reflex Neurohormone reflex 1 2 Stimulus Neuroendocrine reflexes 3 4 Stimulus Receptor Afferent neuron Neurotransmitter Efferent neuron Neurotransmitter Neurohormone Target cell Blood vessel Endocrine cells Response Hormone Response KEY Stimulus Efferent pathways Receptor (sensor) Efferent neuron Sensory neuron (afferent pathway) Neurotransmitter CNS integrating center Endocrine integrating center Response Neurohormone Classic hormone Target cell (effector) Figure 6 -31, steps 1– 4

Control Pathways: Review Simple neural reflex Neurohormone reflex 1 2 Stimulus Neuroendocrine reflexes 3 4 5 Stimulus Receptor Afferent neuron Neurotransmitter Efferent neuron Neurotransmitter Neurohormone Target cell Blood vessel Endocrine cells Response Hormone Response KEY Stimulus Efferent pathways Receptor (sensor) Efferent neuron Sensory neuron (afferent pathway) Neurotransmitter CNS integrating center Endocrine integrating center Hormone #2 Response Neurohormone Classic hormone Target cell (effector) Response Figure 6 -31, steps 1– 5

Control Pathways: Review Simple neural reflex Neurohormone reflex 1 2 Stimulus Simple endocrine reflex Neuroendocrine reflexes 3 4 5 6 Stimulus Receptor Afferent neuron Neurotransmitter Efferent neuron Neurotransmitter Neurohormone Response Target cell Blood vessel Endocrine cells Response Hormone Response KEY Stimulus Efferent pathways Receptor (sensor) Efferent neuron Sensory neuron (afferent pathway) Neurotransmitter CNS integrating center Endocrine integrating center Hormone #2 Response Neurohormone Classic hormone Target cell (effector) Response Figure 6 -31, steps 1– 6

Control Pathways: Review Table 6 -5

Summary • Cell-to-cell communication • Electrical signals • Chemical signals • Four methods

Summary • Signal pathways • • Signal transduction Amplification Second messengers Receptor-enzymes G-proteins Integrin Ligand-gated ion channels

Summary • Novel signal molecules • • • Calcium NO CO H 2 S Lipids • Modulation of signal pathways • Agonist versus antagonist • Up-regulation and down-regulation

Summary • Control pathways • • Cannon’s postulates Local control Reflex control Feedback loops • • Negative feedback Positive feedback Feedforward control Circadian rhythms